1.先化简再求值.[(x+1/2y)^2+(x-1/2y)^2](2x^2-1/2y^2),其中x=-3,y=42.小明在化简A-(ab+2bc-4ac)时,由于马虎,将"A-"写成"A+",得到的结果是3ab-2ac+5bc,问:正确的结果是多少?
来源:学生作业帮助网 编辑:作业帮 时间:2024/08/02 11:00:38
![1.先化简再求值.[(x+1/2y)^2+(x-1/2y)^2](2x^2-1/2y^2),其中x=-3,y=42.小明在化简A-(ab+2bc-4ac)时,由于马虎,将](/uploads/image/z/13939103-47-3.jpg?t=1.%E5%85%88%E5%8C%96%E7%AE%80%E5%86%8D%E6%B1%82%E5%80%BC.%5B%28x%2B1%2F2y%29%5E2%2B%28x-1%2F2y%29%5E2%5D%282x%5E2-1%2F2y%5E2%29%2C%E5%85%B6%E4%B8%ADx%3D-3%2Cy%3D42.%E5%B0%8F%E6%98%8E%E5%9C%A8%E5%8C%96%E7%AE%80A-%28ab%2B2bc-4ac%29%E6%97%B6%2C%E7%94%B1%E4%BA%8E%E9%A9%AC%E8%99%8E%2C%E5%B0%86%22A-%22%E5%86%99%E6%88%90%22A%2B%22%2C%E5%BE%97%E5%88%B0%E7%9A%84%E7%BB%93%E6%9E%9C%E6%98%AF3ab-2ac%2B5bc%2C%E9%97%AE%3A%E6%AD%A3%E7%A1%AE%E7%9A%84%E7%BB%93%E6%9E%9C%E6%98%AF%E5%A4%9A%E5%B0%91%3F)
1.先化简再求值.[(x+1/2y)^2+(x-1/2y)^2](2x^2-1/2y^2),其中x=-3,y=42.小明在化简A-(ab+2bc-4ac)时,由于马虎,将"A-"写成"A+",得到的结果是3ab-2ac+5bc,问:正确的结果是多少?
1.先化简再求值.
[(x+1/2y)^2+(x-1/2y)^2](2x^2-1/2y^2),其中x=-3,y=4
2.小明在化简A-(ab+2bc-4ac)时,由于马虎,将"A-"写成"A+",得到的结果是3ab-2ac+5bc,问:正确的结果是多少?
1.先化简再求值.[(x+1/2y)^2+(x-1/2y)^2](2x^2-1/2y^2),其中x=-3,y=42.小明在化简A-(ab+2bc-4ac)时,由于马虎,将"A-"写成"A+",得到的结果是3ab-2ac+5bc,问:正确的结果是多少?
[(x+1/2y)^2+(x-1/2y)^2](2x^2-1/2y^2),其中x=-3,y=4
[(x+1/2y)^2+(x-1/2y)^2](2x^2-1/2y^2)
=(x^2+xy+1/4y^2+x^2-xy+1/4y^2)(2x^2-1/2y^2)
=(2x^2+1/2y^2)(2x^2-1/2y^2)
=4x^4-1/4y^4
当x=-3,y=4时
原式=4*(-3)^4-1/4*4^4
=324-64
=260
2.小明在化简A-(ab+2bc-4ac)时,由于马虎,将"A-"写成"A+",得到的结果是3ab-2ac+5bc,问:正确的结果是多少?
A+(ab+2bc-4ac)=3ab-2ac+5bc
A=2ab+2ac+3bc
所以
A-(ab+2bc-4ac)
=2ab+2ac+3bc-ab-2bc+4ac
=ab+6ac+bc
1.
2.